Yesterday at Lerer Ventures' CEO Summit, The Facebook Effect author David Kirkpatrick asked two founders, "What's the hardest thing you've ever had to do for your company?"

Both CEOs agreed: it was firing people.

Akshay Kothari, CEO and co-founder of news reader Pulse, said firing someone for the first time was "emotionally traumatizing."

"I've done it twice now. The first one was really hard. But an advisor told me, 'It's not going to be your last fire. You have to do these things and make tough decisions for your company.' It was a good learning experience."

Jonty Kelt of Group Commerce had to fire two people on a management team of eight but says it was "absolutely the right thing to do."

"I learned how important it is to cut the person quickly," says Kelt. "A players don't like working with B players, so if you don't cut those people quickly you actually risk losing your best people."

Kelt also says it's hard to resist hiring someone who isn't quite a fit when you're desperate to fill a position, but it has to be done. "Otherwise you'll hire an asshole," says Kelt.